Nested Mach-Zehnder Interferometer Research Articles

Photons are lying about where they have been, again

Bhati and Arvind (2022) [5] recently argued that in a specially designed experiment the timing of photon detection events demonstrates photon presence at a location at which they are not present according to the weak value approach. The alleged contradiction is resolved by a subtle interference effect resulting in anomalous sensitivity of the signal imprinted on the postselected photons for the interaction at this location, similarly to the case of a nested Mach-Zehnder interferometer with a Dove prism (Alonso and Jordan (2015) [7]). We perform an in-depth analysis of the characterization of the presence of a pre- and postselected particle at a particular location based on information imprinted on the particle itself. The theoretical results are tested by a computer simulation of the proposed experiment.

Hexagonal optical lattices formed by coherent interference among three fundamental Gaussian beams with oblique incidence

Hexagonal optical lattices (HOLs) are formed when three beams with oblique incidence coherently interfere with each other. Theoretical model considering the orientation of three fundamental Gaussian beams is established to describe all kinds of patterns of HOLs. The formula describing the size and shape of the HOLs are also given. The nested Mach-Zehnder interferometer is employed to generate HOLs in experiment. The relations between the geometry parameters (size and shape) of HOLs and orientations of three beams are experimentally and numerically investigated. The experimental generated HOLs can be well simulated using our theory. Our study about HOLs generated by three-beam interference can be used to fabricate periodic structure modulation for the refractive index of a nonlinear media or create two-dimensional photonic crystals.

Hiding the which-path information of photons

Which-path information of a quantum particle in interferometers is the key to infer the past of quantum particle. It arises many extensive discussions including quantum complementarity and path-visibility relation. The basic of these discussions are the description, detection and control of which-path information. In this article, we focus on the investigation of multidimensional which-path information in nested Mach-Zehnder interferometer. A general expression of which-path information is given and can be partially extracted by different detection method. Further analysis shows that the which-path information can be controlled by the phase differences and beam splitting ratios between the arms of nested Mach-Zehnder interferometer. Moreover, a new which-path information elimination phenomenon has been predicted and demonstrated experimentally. Our work can help to understand the physics of quantum particles, potentially apply to quantum information process and quantum metrology.

Scalability of Multi-Stage Nested Mach-Zehnder Interferometer Optical Switch with Phase Generating Couplers

Scalability of Multi-Stage Nested Mach-Zehnder Interferometer Optical Switch with Phase Generating Couplers

Photons can hide where they have been

Recently, the nested Mach–Zehnder interferometer [Phys. Rev. Lett. 111, 240402 (2013)] was modified by adding Dove prisms in a paper [Quantum Stud.: Math. Found. 2, 255 (2015)], and an interesting result is that, after the Dove prisms were inserted, a signal at the first mirror of the nested interferometer was obtained. But, according to the former original paper, the photons have never been present near that mirror. In this work, we interpret this result naturally by resorting to the three-path interference method. Moreover, we find that even though the photons have been somewhere, they can hide the trace of being there.

Nested Mach–Zehnder interferometer optical switch with phase generating couplers

In reconfigurable optical networks, an optical switch is indispensable to afford routing optical signals without optical/electrical conversion. A nested Mach–Zehnder interferometer (MZI) optical switch is suitable for a silicon-silica hybrid structure compared with a conventional cascaded MZI switch. We proposed to employ phase generating couplers (PGCs) instead of directional couplers (DCs) in the nested MZI optical switch. Calculation results show that the nested MZI switch with PGCs exhibits <−30 dB crosstalk over wider wavelength range than that using DCs.

Analysis of single-particle nonlocality through the prism of weak measurements

Although regarded today as an important resource in quantum information, nonlocality has yielded over the years many conceptual conundrums. Among the latter are nonlocal aspects of single particles which have been of major interest. In this paper, the nonlocality of single quanta is studied in a square nested Mach–Zehnder interferometer with spatially separated detectors using a delayed choice modification of quantum measurement outcomes that depend on the complex-valued weak values. We show that if spacelike separated Bob and Alice are allowed to freely control their quantum devices, the geometry of the setup constrains the local hidden variable models. In particular, hidden signaling and a list of contextual instructions are required to split a quantum state characterized by a positive Wigner function into two quantum states with nonpositive Wigner functions. This implies that local hidden variable models could rely neither on only two hidden variables for position and momentum, nor on simultaneous factorizability of both the hidden probability densities and weights of splitting to reproduce the correct quantum distributions. While our analysis does not fully exclude the existence of nonfactorizable local hidden variable models, it demonstrates that the recently proposed weak values of quantum histories necessitate contextual splitting of prior commitments to measurement outcomes, due to functional dependence on the total Feynman sum that yields the complex-valued quantum probability amplitude for the studied quantum transition. This analysis also highlights the quantum nature of weak measurements.

Three-path interference of a photon and reexamination of the nested Mach-Zehnder interferometer

We present a three-path photon interferometer, theoretically investigate the behavior of the photon passing through it, and revisit the surprising experimental outcomes introduced by Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)]. Our study shows that the ``discontinuous trajectory'' behavior of the photon results from the interference of the three propagation paths of the photon, which originate from the light source and end in the detector. If two of the three paths are adjusted in a destructive interference condition, there will be a zero probability domain in the overlap region of these two paths. However, these two paths can still individually interfere with the third path and contribute to the final output. In this condition, the discontinuous trajectory phenomenon appears. Our theory has a clear physical image and agrees with the experimental outcomes very well.

When Photons Are Lying about Where They Have Been.

The history of photons in a nested Mach–Zehnder interferometer with an inserted Dove prism is analyzed. It is argued that the Dove prism does not change the past of the photon. Alonso and Jordan correctly point out that an experiment by Danan et al. demonstrating the past of the photon in a nested interferometer will show different results when the Dove prism is inserted. The reason, however, is not that the past is changed, but that the experimental demonstration becomes incorrect. The explanation of a signal from the place in which the photon was (almost) not present is given. Bohmian trajectory of the photon is specified.

Spectra in nested Mach–Zehnder interferometer experiments

By the means of the standard quantum mechanics formalism I present an explicit derivation of the structure of power spectra in Danan et al. and Zhou et al. experiments with nested dynamically changing Mach–Zehnder interferometers. The analysis confirms that we observe prominent, first-order peaks on frequencies related to some of the elements of the interferometer, but not on others. However, as I shall demonstrate, there are also other, weaker effects related to all relevant elements of the setup. In case of the Danan et al. setup, there are even peaks at all frequencies of element oscillations. When confronted in an experiment, these observations shall challenge the interpretation of the experiments based on anomalous trajectories of light.

Reply to “Comment on ‘Particle path through a nested Mach-Zehnder interferometer' ”

While much of the technical analysis in the preceding Comment [1] is correct, in the end it confirms the conclusion reached in my previous work [2]: a consistent histories analysis provides no support for the claim of counterfactual quantum communication put forward in [3]

Comment on “Particle path through a nested Mach-Zehnder interferometer”

In a recent paper, arXiv:1604.04596, Griffiths questioned - based on an informative consistent-histories (CH) argument - the counterfactuality, for one of the bit choices, of Salih et al.'s protocol for communicating without sending physical particles, Phys. Rev. Lett. 110, 170502 (2013). Here, we first show that for the Mach-Zehnder version used to explain our protocol, no family of consistent histories exists where any history has the photon travelling through the communication channel, thus rendering the question of whether the photon was in the communication channel meaningless from a CH viewpoint. We then show that for the actual Michelson-type protocol, there are consistent-histories families that include histories where the photon travels through the communication channel. We show that the probability of finding the photon in the communication channel is zero - thus proving complete counterfactuality.

High-performance silicon photonic tri-state switch based on balanced nested Mach-Zehnder interferometer

AbsatrctThis work proposes a novel silicon photonic tri-state (cross/bar/blocking) switch, featuring high-speed switching, broadband operation, and crosstalk-free performance. The switch is designed based on a 2 × 2 balanced nested Mach-Zehnder interferometer structure with carrier injection phase tuning. As compared to silicon photonic dual-state (cross/bar) switches based on Mach-Zehnder interferometers with carrier injection phase tuning, the proposed switch not only has better performance in cross/bar switching but also provides an extra blocking state. The unique blocking state has a great advantage in applications of N × N switch fabrics, where idle switching elements in the fabrics can be configured to the blocking state for crosstalk suppression. According to our numerical experiments on a fully loaded 8 × 8 dilated Banyan switch fabric, the worst output crosstalk of the 8 × 8 switch can be dramatically suppressed by more than 50 dB, by assigning the blocking state to idle switching elements in the fabric. The results of this work can extend the functionality of silicon photonic switches and significantly improve the performance of on-chip N × N photonic switching technologies.

Reply to “Comment on ‘Particle path through a nested Mach-Zehnder interferometer’ ”

The correctness of the consistent histories analysis of weakly interacting probes, related to the path of a particle, is maintained against the criticisms in the Comment, and against the alternative approach described there, which receives no support from standard (textbook) quantum mechanics.

Comment on “Particle path through a nested Mach-Zehnder interferometer”

Griffiths [Phys. Rev. A 94, 032115 (2016)] analyzed, in the framework of a consistent histories interpretation, the controversy regarding the approach to the past of a quantum particle introduced by Vaidman [Phys. Rev. A 87, 052104 (2013)]. I argue that Griffith's criticism of my approach using an analysis of experiments with weak probes is unfounded.

Response to the comment on “Paradox of photons disconnected trajectories being located by means of ‘weak measurements’ in the nested Mach–Zehnder interferometer” (JETP Letters 105, 152 (2017))

In [JETP Lett. 105(3), 152 (2017)], a clear and comprehensive analysis of the paradoxical results of experiment [Phys. Rev. Lett. 111, 240402 (2013)] was carried out on the basis of the classical wave theory of light, which presupposes the continuity of possible of light paths. It was shown that the paradoxical results of the experiment are due not to the discontinuity of the trajectories of light, as claimed in [Phys. Rev. Lett. 111, 240402 (2013)], but to the used way of detecting the path of photons. The experiment modification proposed in [JETP Lett. 105(3), 152 (2017)] allows us to eliminate the seeming discontinuity of the light trajectories. In Comment [arXiv:1705.02137 (2017)] to the article such modification is declared unreasonable. This Response to the Comment shows that this statement is not based on clear and logical arguments. Instead, it is only asserted that the proposed modification "violates the faithfulness indication of the trace" of photons. Therefore, the Comment's criticism can not be considered as well-founded. Consequently, the conclusion of [JETP Lett. 105(3), 152 (2017)] that a new concept of disconnected trajectories proposed by the authors of work [Phys. Rev. Lett. 111, 240402 (2013)] is unnecessary, remains valid.

Comment on “Paradox of photons disconnected trajectories being located by means of ‘weak measurements’ in the nested Mach–Zehnder interferometer” (JETP Letters 105, 152 (2017))

The criticism of the experiment showing discontinuous traces of photons passing through a nested Mach-Zehnder interferometer is shown to be unfounded.

Paradox of photons disconnected trajectories being located by means of “weak measurements” in the nested Mach–Zehnder interferometer

Recently, a scheme based on the method of weak measurements to register the trajectories of photons passing through a nested Mach-Zehnder interferometer was proposed [L. Vaidman, Phys. Rev. A \textbf{87}, 052104 (2013)] and then realized [A. Danan, D. Farfurnik, S. Bar-Ad, et al., Phys. Rev. Lett. \textbf{111}, 240402 (2013)]. Interpreting the results of the experiment, the authors concluded that "the photons do not always follow continuous trajectories". It is shown in this work that these results can be easily and clearly explained in terms of traditional classical electrodynamics or quantum mechanics implying the continuity of all possible paths of photons. Consequently, a new concept of disconnected trajectories proposed by the authors of work [Phys. Rev. Lett. \textbf{111}, 240402 (2013)] is unnecessary.

An Improved Experiment to Determine the ‘Past of a Particle’ in the Nested Mach–Zehnder Interferometer**Supported by the German-Israeli Foundation for Scientific Research and Development under Grant No I-1275-303.14.

We argue that the modification proposed by Li et al. [Chin. Phys. Lett. 32 (2015) 050303] to the experiment of Danan et al. [Phys. Rev. Lett. 111 (2013) 240402] does not test the past of the photon as characterized by local weak traces. Instead of answering the questions: (i) were the photons in A? (ii) were the photons in B? and (iii) were the photons in C? the proposed experiment measures a degenerate operator answering the questions: (i) were the photons in A? and (ii) were the photons in B and C together? A negative answer to the last question does not tell us if photons were present in B or C. On the other hand, a simple variation of the proposal by Li et al. does provide conceptually better evidence for the past of the pre- and post-selected photon, but this evidence will be in agreement with the results of Danan et al.

Reconfigurable Silicon Photonics Integrated 16-QAM Modulator Driven by Binary Electronics

A novel silicon photonics integrated reconfigurable nested Mach–Zehnder interferometer including tunable splitters and four independent phase modulators has been designed and fabricated. The architecture enables the generation of offset-free phase–amplitude constellations such as QPSK and 16-QAM by employing simple binary signals with equal peak-to-peak amplitude. The adoption of tunable splitters introduces novel features such as reconfiguration of the output constellation without modification of the RF waveform settings, as well as compensation for imperfections related to fabrication tolerances. The solution presented in this paper is based on travelling wave MZIs and thermally tunable splitters based on doped rib waveguides heated by Joule effect. The scheme minimizes the complexity of the employed architecture together with one of the driving signals. Numerical analysis has been also conducted to better investigate the system behavior and parameter optimization, evaluating the impact of suboptimum settings that might occur in a real implementation. Experimental results show the generation of QPSK signals up to 28 Gbd and 16-QAM signals up to 20 Gbd with measured bit error rate below the conventional FEC level.